Question

A manufacturer produces digital watches. Every two hours a sample of six watches is selected randomly to be tested. Each watch is run for exactly 15 minutes and is timed by an accurate, precise timing device. Because of the variation among watches, they do not all run the same. Shown here are the data from eight different samples given in minutes. Use these data to construct x̄ and R charts. Observe the results and comment on whether the process is incontrol.